Adhesive of epoxy resin and curing agent with xylylene diamine structure

ABSTRACT

The present invention provides an adhesive for laminates containing, as a main component, an epoxy resin composition comprising an epoxy resin and an epoxy resin-curing agent, the epoxy resin composition being formed into an epoxy resin cured product containing a skeleton structure represented by the formula (1): 
                         
in an amount of at least 40% by weight. Since the adhesive of the present invention reveals not only a suitable adhesion to various film materials but also a high gas-barrier property, only a single layer formed therefrom can realize both an excellent gas-barrier property and an excellent adhesion property in combination, so that it is possible to produce a high gas-barrier laminated film for a packaging material without forming a separate gas-barrier layer therein.

TECHNICAL FIELD

The present invention relates to an adhesive for laminates which have ahigh gas-barrier property and a suitable adhesion to film materials suchas various polymers, papers and metals, as well as a laminated film, amulti-layer packaging material and a packaging bag using the adhesive.

BACKGROUND ART

In recent years, packaging materials have been predominantly preparedfrom composite flexible films made of different kinds of polymermaterials in combination because of their strength, goods-protectingproperty, workability, advertising effects provided by printing or so,etc. The composite flexible films are generally constituted from athermoplastic resin film, etc., which serves an outer layer forprotecting goods, and another thermoplastic resin film, etc., whichserves as a sealant layer. These layers are laminated together by adry-lamination method in which the sealant layer is bonded to alaminated film layer through an adhesive applied to the laminated filmlayer, or by an extrusion lamination method in which a melt-extrudedplastic film as the sealant layer is pressure-stuck with the laminatedfilm layer which may be optionally coated with an anchor coat agent,thereby laminating the sealant layer over the laminated film layer in aform of film. In these methods, two-part liquid polyurethane-basedadhesives that are generally composed of a main ingredient comprising anactive hydrogen-containing group such as hydroxyl group, and anisocyanate group-containing curing agent, have been predominantly usedas the adhesives in view of a high adhesion property thereof (forexample, refer to Japanese Patent Application Laid-open Nos. Hei 5-51574and Hei 9-316422, etc.).

However, these two-part liquid polyurethane-based adhesives generallyexhibit a slow curing reaction rate. Therefore, in order to ensure asufficient adhesion property of the two-part liquid polyurethane-basedadhesives, the resultant laminated film must be aged for a long periodof time, e.g., 1 to 5 days after the lamination, for promoting thecuring reaction. Also, since the curing agent comprising isocyanategroups is used in the two-part liquid polyurethane-based adhesives, whenresidual unreacted isocyanate groups are present therein after curing,there may occur problems such as generation of bubbles in the resultantlaminated film which is attributed to carbon dioxide formed by thereaction between the residual unreacted isocyanate groups in theadhesives and moisture in atmospheric air.

On the other hand, in order to overcome the above problems, JapanesePatent Application Laid-open No. 2000-154365 has proposedpolyurethane-based adhesives, and WO 99/60068 has proposed epoxy-basedadhesives for laminate.

However, the above polyurethane-based adhesives as well as theepoxy-based adhesives proposed in WO 99/60068 reveal a low gas-barrierproperty. Therefore, when these adhesives are employed for packagingmaterials requiring a high gas-barrier property, it is necessary toseparately laminate additional various gas-barrier layers such as a PVDCcoating layer, a polyvinyl alcohol (PVA) coating layer, anethylene-vinyl alcohol copolymer (EVOH) film layer, am-xylyleneadipamide film layer and an inorganic deposited film layer onwhich alumina (Al₂O₃), silica (Si) or the like is vapor-deposited, whichresults in high production costs of laminated films or disadvantageouslaminating processes.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an adhesive forgas-barrier laminates which exhibit a high gas-barrier property and toprovide the adhesive having an excellent adhesion property to variouspolymers, papers, metals, etc., as well as a gas-barrier laminated filmusing the adhesive.

As a result of extensive researches for overcoming the above problems,the present inventors have found that an adhesive composed mainly of aspecific epoxy resin composition exhibits not only a high gas-barrierproperty but also a suitable adhesion property to various polymers,papers, metals, etc. The present invention has been accomplished on thebasis of this finding.

That is, the present invention provides an adhesive for laminatescontaining as a main component, an epoxy resin composition comprising anepoxy resin and an epoxy resin-curing agent, the epoxy resin compositionbeing formed into an epoxy resin cured product containing a skeletonstructure represented by the formula (1):

in an amount of at least 40% by weight. The present invention alsoprovides a laminated film, a multi-layer packaging material and apackaging bag using the adhesive.

PREFERRED EMBODIMENTS TO CARRY OUT THE INVENTION

The adhesive for laminates according to the present invention containsas a main component, an epoxy resin composition including an epoxy resinand an epoxy resin-curing agent. The epoxy resin cured product formedfrom the epoxy resin composition contains the skeleton structurerepresented by the above formula (1) in an amount of at least 40% byweight, preferably at least 45% by weight and more preferably at least50% by weight. The high-level content of the skeleton structurerepresented by the formula (1) in the epoxy resin cured product formingan adhesive layer enables the resultant laminated film to reveal a highgas-barrier property. First, the epoxy resin and the epoxy resin-curingagent which form the epoxy resin cured product are explained below.

(Epoxy Resin)

The epoxy resin used in the adhesive for laminates according to thepresent invention may be any of aliphatic compounds, alicycliccompounds, aromatic compounds and heterocyclic compounds. In view of ahigh gas-barrier property, among these resins, preferred are epoxyresins containing aromatic moieties in a molecule thereof, and morepreferred are epoxy resins containing the above skeleton structurerepresented by the formula (1) in a molecule thereof.

Specific examples of such an epoxy resin include epoxy resins containingglycidylamine moieties derived from m-xylylenediamine, epoxy resinscontaining glycidylamine moieties derived from1,3-bis(aminomethyl)cyclohexane, epoxy resins containing glycidylaminemoieties derived from diaminodiphenylmethane, epoxy resins containingglycidylamine moieties and/or glycidyl ether moieties derived fromp-aminophenol, epoxy resins containing glycidyl ether moieties derivedfrom bisphenol A, epoxy resins containing glycidyl ether moietiesderived from bisphenol F, epoxy resins containing glycidyl ethermoieties derived from phenol novolak, epoxy resins containing glycidylether moieties derived from resorcinol, or the like. Of these epoxyresins, preferred are epoxy resins containing glycidylamine moietiesderived from m-xylylenediamine, epoxy resins containing glycidylaminemoieties derived from 1,3-bis(aminomethyl)cyclohexane, epoxy resinscontaining glycidyl ether moieties derived from bisphenol F and epoxyresins containing glycidyl ether moieties derived from resorcinol.

Further, the epoxy resin used in the adhesive for laminates according tothe present invention more preferably contains as a main component theepoxy resin containing glycidyl ether moieties derived from bisphenol For the epoxy resin containing glycidylamine moieties derived fromm-xylylenediamine, and most preferably contains the epoxy resincontaining glycidylamine moieties derived from m-xylylenediamine.

In addition, the epoxy resin may also be used in the form of a mixturecontaining any two or more of the above-described epoxy resins atappropriate blending ratios, in order to improve various properties ofthe resultant product such as flexibility, impact resistance and wetheat resistance.

The epoxy resin used in the present invention is produced by reactingvarious alcohols, phenols and amines with epihalohydrin. For example,the epoxy resins containing glycidylamine moieties derived fromm-xylylenediamine are produced by the addition reaction ofepichlorohydrin to m-xylylenediamine.

Here, the above glycidylamine moieties include mono-, di-, tri- and/ortetra-glycidylamine moieties that can be substituted with four hydrogenatoms of diamine in the xylylenediamine. The ratio between the mono-,di-, tri- and/or tetra-glycidylamine moieties can be altered by changingthe ratio between m-xylylenediamine and epichlorohydrin to be reacted.For example, epoxy resins containing mainly tetra-glycidylamine moietiesare obtained by the addition reaction in which about 4 mol ofepichlorohydrin is added to one mol of m-xylylenediamine.

More specifically, the epoxy resin used in the present invention issynthesized by reacting various alcohols, phenols and amines with anexcess amount of epihalohydrin in the presence of an alkali such assodium hydroxide at a temperature of 20 to 140° C. and preferably 50 to120° C. for the alcohols and phenols, and 20 to 70° C. for the amines,and then separating the resultant alkali halide from the reactionmixture.

The number-average molecular weight of the thus produced epoxy resinvaries depending upon the molar ratio of epichlorohydrin to variousalcohols, phenols and amines, and is about 80 to 4,000, preferably about200 to 1,000 and more preferably about 200 to 500.

(Epoxy Resin-Curing Agent)

The epoxy resin-curing agent used in the adhesive for laminatesaccording to the present invention may be any of aliphatic compounds,alicyclic compounds. aromatic compounds and heterocyclic compounds.Namely, as the epoxy resin-curing agent, there may be used thoseordinarily used for curing epoxy resins such as polyamines, phenols,acid anhydrides and carboxylic acids. The epoxy resin-curing agent maybe appropriately selected according to applications of the resultantlaminated film as well as its properties required for the applications.

Specific examples of the polyamines as the epoxy resin-curing agentinclude aliphatic amines such as ethylenediamine, diethylenetriamine,triethylenetetramine and tetraethylenepentamine; aromaticring-containing aliphatic amines such as m-xylylenediamine andp-xylylenediamine; alicyclic amines such as1,3-bis(aminomethyl)cyclohexane, isophoronediamine andnorbornanediamine; and aromatic amines such as diaminodiphenylmethaneand m-phenylenediamine.

Further, as the epoxy resin-curing agent, there may also be used epoxyresins produced using these polyamines as raw materials, or modifiedreaction products of these polyamines with a monoglycidyl compound,modified reaction products of these polyamines with C₂ to C₄alkyleneoxide, addition products of these polyamines withepichlorohydrin, reaction products of these polyamines with apolyfunctional compound having at least one acyl group which is capableof forming amido moieties and, as a result, an oligomer by the reactionwith the polyamines, reaction products of these polyamines with apolyfunctional compound having at least one acyl group which is capableof forming amido moieties and, as a result, an oligomer by the reactionwith the polyamines, and a monocarboxylic acid and/or its derivative, orthe like.

Examples of the phenols include poly-substituted monomers such ascatechol, resorcinol and hydroquinone, resol-type phenol resins or thelike.

In addition, as the acid anhydrides or carboxylic acids, there may beused aliphatic acid anhydrides such as dodecenyl succinic anhydride andpoly-adipic anhydride; alicyclic acid anhydrides such as(methyl)tetrahydrophthalic anhydride and (methyl)hexahydrophthalicanhydride; aromatic acid anhydrides such as phthalic anhydride,trimellitic anhydride and pyromellitic anhydride; correspondingcarboxylic acids of these anhydrides; or the like.

In view of a high bas-barrier property of the obtained cured product, ofthese epoxy resin-curing agents, preferred are epoxy resin-curing agentscontaining aromatic moieties in a molecule thereof, and more preferredare epoxy resin-curing agents having a skeleton structure represented bythe foregoing formula (1) in a molecule thereof.

More specifically, as the epoxy resin-curing agents, there are morepreferably used m-xylylenediamine or p-xylylenediamine, as well as epoxyresins produced using these polyamines as raw materials, or modifiedreaction products of these polyamines with a monoglycidyl compound,modified reaction products of these polyamines with a C₂ to C₄alkyleneoxide, addition products of these polyamines withepichlorohydrin, reaction products of these polyamines with apolyfunctional compound having at least one acyl group which is capableof forming amido moieties and, as a result, an oligomer by the reactionwith the polyamines, reaction products of these polyamines with apolyfunctional compound having at least one acyl group which is capableof forming amido moieties and, as a result, an oligomer by the reactionwith the polyamines, and a monocarboxylic acid and/or its derivative, orthe like.

In view of a high gas-barrier property and a good adhesion to variousfilm materials, the epoxy resin-curing agent is especially preferablycomposed of reaction products of the following components (A) and (B),or reaction products of the following components (A), (B) and (C):

(A) m-xylylenediamine and/or p-xylylenediamine;

(B) a polyfunctional compound having at least one acyl group which iscapable of forming amido moieties and, as a result, an oligomer by thereaction with the polyamines; and

(C) a C₁ to C₈ monocarboxylic acid and/or its derivative.

Examples of the polyfunctional compound having at least one acyl groupwhich is capable of forming amido moieties and, as a result, an oligomerby the reaction with the polyamines, include carboxylic acids such asacrylic acid, methacrylic acid, maleic acid, fumaric acid, succinicacid, malic acid, tartaric acid, adipic acid, isophthalic acid,terephthalic acid, pyromellitic acid and trimellitic acid; derivativesof these carboxylic acids such as esters, amides, acid anhydrides andacid chlorides thereof, or the like. Of these polyfunctional compounds,preferred are acrylic acid, methacrylic acid and derivatives thereof.

Also, the C₁ to C₈ monocarboxylic acid such as formic acid, acetic acid,propionic acid, butyric acid, lactic acid, glycolic acid and benzoicacid, or its derivative such as esters, amides, acid anhydrides and acidchlorides of these acids together with the above polyfunctional compoundmay be reacted with the polyamine as the starting material. The amidomoieties introduced into the epoxy resin-curing agent by the reactionhave a high coagulation force. Therefore, when such amido moieties arepresent at a high content in the epoxy resin-curing agent, the resultantadhesive layer can reveal a higher oxygen-barrier property and a goodadhesion strength to various film materials.

The molar ratio between the components (A) and (B) to be reacted, orbetween the components (A), (B) and (C) to be reacted may be adjustedsuch that the ratio of the number of reactive functional groupscontained in the component (B) to the number of amino groups containedin the component (A), or the ratio of the total number of reactivefunctional groups contained in the components (B) and (C) to the numberof amino groups contained in the component (A), is preferably in therange of 0.3 to 0.97.

When the above ratio of the reactive functional groups is less than 0.3,a sufficient amount of amido groups are not produced in the epoxyresin-curing agent, so that the resultant cured product may fail to showa high gas-barrier property and a good adhesion strength to various filmmaterials. In addition, since the content of residual volatile moleculesin the epoxy resin-curing agent increases, the resultant cured producttends to suffer from generation of malodor. Further, since the contentof hydroxyl groups in the cured product which are produced by thereaction between epoxy groups and amino groups also increases, theresultant cured product tends to be considerably deteriorated inoxygen-barrier property under high-humidity environmental conditions.

On the other hand, when the ratio of the reactive functional groupsexceeds 0.97, the amount of amino groups in the epoxy resin-curing agentwhich can be reacted with the epoxy resin becomes small, so that theresultant cured product may fail to reveal excellent impact resistanceand heat resistance, and also tends to be deteriorated in solubility invarious organic solvent and water.

In order to obtain a cured product capable of showing a high gas-barrierproperty and a high adhesion strength, preventing the generation ofmalodor therefrom and revealing a high oxygen-barrier property underhigh-humidity environmental conditions, the molar ratio of thepolyfunctional compound to the polyamine component is more preferably inthe range of 0.67 to 0.97. Further, in view of a still higher adhesionstrength to various film materials, the epoxy resin-curing agent used inthe present invention preferably contains the amido groups in an amountof at least 6% by weight based on the total weight of the curing agent.

A laminated film produced using the adhesive for laminates according tothe present invention preferably has an initial tacking force of 30 g/15mm or greater, more preferably 40 g/15 mm or greater and most preferably50 g/15 mm or greater as measured between film materials thereof bysubjecting the laminated film to T-peel test at a peel velocity of 300mm/min immediately after the lamination. If the initial tacking forcebetween the respective film materials of the laminated film isinsufficient, the laminated film tends to suffer from problems such astunneling and winding disorder of the film upon winding-up thereof.

In order to allow the laminated film to reveal a high tackiness betweenthe film materials thereof, for example, the reaction product ofm-xylylenediamine or p-xylylenediamine with the polyfunctional compoundhaving at least one acyl group which is capable of forming amidomoieties and, as a result, an oligomer by the reaction with thepolyamines, as the epoxy resin-curing agent, is controlled in reactionratio such that the molar ratio of the polyfunctional compound to thepolyamine component is in the range of 0.6:1 to 0.97:1, preferably 0.8:1to 0.97 and more preferably 0.85:1 to 0.97:1. In addition, it ispreferable to use such an epoxy resin-curing agent composed of theoligomer as the above reaction product which is increased in its averagemolecular weight.

The more preferred epoxy resin-curing agent is a reaction product ofm-xylylenediamine with acrylic acid, methacrylic acid and/or aderivative thereof. The reaction molar ratio of the acrylic acid,methacrylic acid and/or a derivative thereof to m-xylylenediamine ispreferably in the range of 0.8:1 to 0.97:1.

(Adhesive for Laminates)

In the adhesive for laminates according to the present invention, theepoxy resin and the epoxy resin-curing agent as main components of theadhesive may be blended at standard ratios that are generally used forproducing an epoxy resin cured product by the reaction between the epoxyresin and epoxy resin-curing agent. More specifically, the ratio of thenumber of active hydrogen atoms in the epoxy resin-curing agent to thenumber of epoxy groups in the epoxy resin is in the range of 0.5:1 to5.0:1. When the above ratio is less than 0.5:1, the resultant cureproduct tends to be deteriorated in gas-barrier property due to residualunreacted epoxy groups. When the ratio exceeds 5.0:1, the resultantcured product tends to be deteriorated in wet heat resistance due toresidual unreacted amino group. In particular, in view of gas-barrierproperty and wet heat resistance of the resultant cured product, theequivalent ratio of active hydrogen atoms in the epoxy resin-curingagent to epoxy groups in the epoxy resin (active hydrogen atoms/epoxygroup) is more preferably in the range of 0.8:1 to 3.0:1 and mostpreferably 0.8:1 to 1.4:1.

Further, in order to allow the resultant cured product to show a highoxygen-barrier property under high-humidity environmental conditions,the equivalent ratio of active hydrogen atoms in the epoxy resin-curingagent to epoxy groups in the epoxy resin is preferably controlled to therange of 0.8:1 to 1.4:1.

The above epoxy resin composition of the present invention mayoptionally contain thermosetting resin compositions such aspolyurethane-based resin compositions, polyacrylic resin compositionsand polyurea-based resin compositions according to the requirementsunless the addition thereof adversely affects the effects of the presentinvention.

The adhesive for laminates according to the present invention may alsooptionally contain a wetting agent such as silicone and acryliccompounds according to the requirements to assist wetting of a surfaceof various film materials upon applying the adhesive thereto. Examplesof the suitable wetting agent include BYK331, BYK333, BYK348 and BYK381available from BYK Chemie GmbH, etc. The wetting agent is preferablyadded in an amount of 0.01% by weight to 2.0% by weight based on thetotal weight of the adhesive composition.

The adhesive for laminates according to the present invention may alsooptionally contain a tackifier such as xylene resins, terpene resins,phenol resins and rosin resins in accordance with the requirements inorder to enhance its tackiness to various film materials immediatelyafter applying the adhesive to the surface of the respective filmmaterials. The tackifier is preferably added in an amount of 0.01% byweight to 5.0% by weight based on the total weight of the adhesivecomposition.

In addition, the adhesive for laminates according to the presentinvention may also contain an inorganic filler such as silica, alumina,mica, talc, aluminum flakes and glass flakes in order to enhance variousproperties such as gas-barrier property, impact resistance and heatresistance of an adhesive layer formed therefrom.

In view of transparency of the resultant film, the inorganic filler ispreferably in the form of a flat plate. The inorganic filler ispreferably added in an amount of 0.01% by weight to 10.0% by weightbased on the total weight of the adhesive composition.

Further, the adhesive for laminates according to the present inventionmay also optionally contain an oxygen-capturing compound according torequirements. Examples of the oxygen-capturing compound includelow-molecular weight organic compounds capable of reacting with oxygensuch as hindered phenols, vitamin C, vitamin E, organophosphoruscompounds, gallic acid and pyrogallol, transition metal compoundscontaining metals such as cobalt, manganese, nickel, iron and copper, orthe like.

In addition, the adhesive for laminates according to the presentinvention may also contain a coupling agent such as silane couplingagents and titanium coupling agents in order to enhance the adhesiveproperty of an adhesive layer formed therefrom to various film materialssuch as plastic films, metal foils and papers. The coupling agent ispreferably added in an amount of 0.01% by weight to 5.0% by weight basedon the total weight of the adhesive composition.

(Film Materials)

Examples of the film materials to be laminated by the adhesive of thepresent invention include polyolefin-based films made of low-densitypolyethylene, high-density polyethylene, linear low-densitypolyethylene, polypropylene, etc., polyester-based films made ofpolyethylene terephthalate, polybutylene terephthalate, etc.,polyamide-based films made of nylon 6, nylon 6.6, m-xylyleneadipamide(N-MXD6), etc., polyacrylonitrile-based films, poly(meth)acrylic films,polystyrene-based films, polycarbonate-based films, ethylene-vinylalcohol copolymer-based films, polyvinyl alcohol-based films, paperssuch as carton, metal foils such as aluminum foils and copper foils,films obtained by coating these film materials with various polymerssuch as polyvinylidene chloride (PVDC) resins, polyvinyl alcohol resins,ethylene-vinyl alcohol (EVOH) copolymer-based resins and acrylic resins,films on which various inorganic compounds or metals such as silica,alumina and aluminum are vapor-deposited, films in which inorganicfillers, etc., are dispersed, oxygen-capturing films, or the like. Also,the above various polymers to be coated on the film materials maycontain inorganic fillers dispersed therein. Examples of such inorganicfillers include silica, alumina, mica, talc, aluminum flakes, glassflakes or the like. Of these inorganic fillers, preferred arephyllosilicates such as montmorillonite. These inorganic fillers may bedispersed in the polymers by known methods such as extrusion-kneadingand mixing-dispersion in resin solutions. In order to impart anoxygen-capturing property to the films, for example, such a compositioncontaining oxygen-reactive low-molecular weight organic compounds suchas hindered phenols, vitamin C, vitamin E, organophosphorus compounds,gallic acid and pyrogallol, transition metal compounds containing metalssuch as cobalt, manganese, nickel, iron and copper, or the like, may beused as a part of the film materials.

The thickness of these film materials is about 10 to 300 μm andpreferably about 10 to 100 μm in view of practical use thereof. Plasticfilms used as the film materials may be monoaxially or biaxiallystretched.

The surface of these film materials is preferably subjected to varioussurface treatments such as flame treatment and corona dischargetreatment, if desired, in order to form thereon an adhesive layer thatis free from defects such as break and repelling. These treatments canpromote a good adhesion of the adhesive layer to various film materials.Further, after subjecting the film materials to an appropriate surfacetreatment, a printed layer may be provided on the surface of the filmmaterials, if desired. The printed layer may be produced by ordinaryprinting apparatuses used for printing on conventional polymer films,such as gravure printing machines, flexographic printing machines andoffset printing machines. As ink that forms the printed layer, there mayalso be employed various inks used for forming a printed layer onconventional polymer films which are composed of pigments such asazo-based pigments and phthalocyanine-based pigments, resins such asrosins, polyamides and polyurethanes, and a solvent such as methanol,ethyl acetate and methyl ethyl ketone.

Among these film materials, the flexible polymer film layer serving asthe sealant layer is preferably selected from polyolefin-based filmssuch as polyethylene film, polypropylene film and ethylene-vinyl acetatecopolymer film in view of a good heat sealability thereof. These filmshave a thickness of about 10 to 300 μm and preferably about 10 to 100 μmin view of practical use thereof, and may also be subjected to varioussurface treatments such as flame treatment and corona dischargetreatment.

(Laminating Method)

Various film materials may be laminated using the adhesive for laminatesaccording to the present invention by known laminating methods such asdry lamination, non-solvent lamination and extrusion lamination.

The laminating method in which the adhesive for laminates according tothe present invention is applied onto the film materials for laminatingthese film materials therethrough may be conducted at a concentration ofthe adhesive composition and a temperature which are sufficient toobtain an epoxy resin cured product as the adhesive layer. Theconcentration of the adhesive composition and the temperature may varydepending upon starting materials and laminating method as selected.More specifically, the concentration of the adhesive composition can bevariously changed over a range of from the condition where no solvent isused to the condition where the composition is diluted to about 5% byweight dilute solution using a certain suitable organic solvent and/orwater, according to kinds and molar ratios of the selected rawmaterials, laminating method, etc.

Examples of the suitable organic solvent include non-aqueous solventssuch as toluene, xylene and ethyl acetate; glycol ethers such as2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol,1-methoxy-2-propanol, 1-ethoxy-2-propanol and 1-propoxy-2-propanol;alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanoland 2-butanol; aprotonic polar solvents such as N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone; or thelike. Of these solvents, preferred are relatively low-boiling solventssuch as methanol, ethyl acetate and 2-propanol.

The adhesive using the solvent may be dried after coating over a broadtemperature range of from room temperature to about 140° C. to removethe solvent therefrom.

The adhesive composition may be applied onto the film materials by anycoating methods ordinarily used for this purpose, such as roll coating,spray coating, air-knife coating, dip coating and brush coating. Ofthese methods, preferred are roll coating and spray coating. Forexample, there may be used the same roll coating and spray coatingtechniques and facilities as used for applying a polyurethane-basedadhesive component onto the film materials to form a laminated film.

Next, specific procedures used in the respective laminating methods areexplained below.

In the dry lamination method, immediately after a dilute solutionprepared by dissolving the adhesive for laminates according to thepresent invention in an organic solvent and/or water is applied onto thesurface of a film material as a substrate using rolls such as gravurerolls and then dried to remove the solvent therefrom, another filmmaterial is laminated thereon by nip rolls, etc., to form a laminatedfilm. In this case, it is preferred that the thus obtained laminatedfilm is aged at a temperature of from room temperature to 60° C. for apredetermined period of time to complete the curing reaction. When theaging is performed for the predetermined period of time, it is possibleto produce an epoxy resin cured reaction product revealing a highgas-barrier property at a sufficient reaction rate.

In the non-solvent lamination method, immediately after the adhesive forlaminates according to the present invention which is previously heatedto a temperature of about 40° C. to 100° C. is applied onto the surfaceof a film material as a substrate using rolls such as gravure rollswhich are also heated to a temperature of 40° C. to 120° C., anotherfilm material is laminated thereon by nip rolls, etc., to form alaminated film. In this case, it is also preferred that the thusobtained laminated film is aged for a predetermined period of timesimilarly to the above dry lamination method.

In the extrusion lamination method, a dilute solution prepared bydissolving the epoxy resin and the epoxy resin-curing agent as maincomponents of the adhesive for laminates according to the presentinvention in an organic solvent and/or water, as an adhesive assistant(anchor coat agent), is applied over the surface of a film material as asubstrate using rolls such as gravure rolls. Then, after the resultantcoated film material is dried at a temperature of from room temperatureto 140° C. to remove the organic solvent therefrom and conduct a curingreaction thereof, a polymer material melted in an extruder is extrudedand laminated thereon to form a laminated film. As the polymer materialto be melt-laminated, polyolefin-based resins such as low-densitypolyethylene resin, linear low-density polyethylene resin andethylene-vinyl acetate copolymer resin may be preferably employed.

In the co-extrusion lamination method, molten polymer materials and theadhesive for laminates according to the present invention are filledinto an extruder, and extruded therefrom into a plurality of layersthrough a cylindrical die or a T-die to form a laminated film. Thestructure of the laminated film and kinds of polymer materials used mayvary depending upon applications of the resultant film and propertiesrequired therefor. Specific examples of the structure of the laminatedfilm include, but are not limited to, a three-layer structure composedof polymer material layer/adhesive layer/polymer material layer, a fivelayer structure composed of polymer material layer/adhesivelayer/polymer material layer/adhesive layer/polymer material layer, orthe like. Also, the adhesive for laminates according to the presentinvention may be used in at least one adhesive layer of the laminatedfilm. In this case, other adhesive layers of the laminated film may bemade of an ordinary polyurethane-based adhesive, etc.

Further, in addition to the above laminating methods, there may be usedsuch a method in which the adhesive for laminates according to thepresent invention is injected between adjacent two film or sheetmaterials to form a laminated film.

These laminating methods may be used in combination with other ordinarylaminating methods, if desired, and the layer structure of the obtainedlaminated film may vary depending upon applications and configurationsthereof.

The adhesive layer obtained after applying the adhesive for laminatesaccording to the present invention over various film materials, followedby drying, lamination and heat-treatment, has a thickness of 0.1 to 100μm and preferably 0.5 to 10 μm in view of practical use of the resultantlaminated film. When the thickness of the adhesive layer is less than0.1 μm, the adhesive layer may fail to exhibit a sufficient gas-barrierproperty and adhesion property. On the other hand, when the thickness ofthe adhesive layer exceeds 100 μm, it may be difficult to form anadhesive layer having a uniform thickness.

(Laminated Film)

The adhesive for laminates according to the present invention can revealnot only a good adhesion property to various film materials but also ahigh gas-barrier property over a broad range of from low-humiditycondition to high-humidity condition. Therefore, the laminated filmproduced using the adhesive for laminates according to the presentinvention can show an extremely high gas-barrier property without usingan ordinarily used gas-barrier material such as PVDC coating layer,polyvinyl alcohol (PVA) coating layer, ethylene-vinyl alcohol copolymer(EVOH) film layer, m-xylyleneadipamide film layer and inorganicdeposited film layer on which alumina (AL₂O₃), silica (Si), etc., isvapor-deposited. In addition, by using the adhesive for laminatesaccording to the present invention as an adhesive for laminating theconventional gas-barrier material and a sealant material, the obtainedlaminated film can be more remarkably improved in gas-barrier property.

Also, gas-barrier films such as saponified ethylene-vinyl acetatecopolymer (EVOH)-based films, polyvinyl alcohol-based films, polyvinylalcohol-coated films, inorganic filler-dispersed polyvinylalcohol-coated films and m-xylyleneadipamide (N-MXD6) films generallytend to be deteriorated in gas-barrier property under high-humiditycondition. However, when the adhesive for laminates according to thepresent invention is used to form a laminated film including thesegas-barrier films, the resultant laminated film can show an improvedgas-barrier property even under the high-humidity condition.

Further, since the epoxy resin cured product forming the adhesive layerin the laminated film of the present invention is excellent in toughnessand wet heat resistance, it also becomes possible to produce agas-barrier laminated film that is excellent in impact resistance,resistance to boiling treatment and resistance to retort treatment.

(Multi-Layer Packaging Material)

The laminated film produced using the adhesive for laminates accordingto the present invention may be employed as a multi-layer packagingmaterial for the purpose of protecting foods, drugs, etc. When thelaminated film of the present invention is used as such a multi-layerpackaging material, the layer structure thereof may vary depending uponcontents as well as environmental conditions and configurations uponuse. More specifically, the laminated film of the present invention maybe directly used as the multi-layer packaging material. Alternatively,an oxygen-absorbing layer, a thermoplastic resin film layer, a paperlayer, a metal foil layer, etc., may be further laminated on thelaminated film of the present invention, if desired. In the latter case,the lamination may be performed using either the adhesive for laminatesaccording to the present invention or the other adhesives or anchor coatagents.

(Packaging Bag)

Next, packaging bags made of a soft packaging bag which is produced fromthe above multi-layer packaging material are explained. The packagingbags made of such a soft packaging bag, etc., can be produced byoverlapping the multi-layer packaging materials such that heat-sealableresin layers thereof face each other, and then heat-sealing theperipheral edge portions of the overlapped multi-layer packagingmaterials to form a sealed portion. As the bag-making method, there maybe used, for example, such a method in which the multi-layer packagingmaterial is folded up or the multi-layer packaging materials areoverlapped so as to face inner layers thereof to each other, and then aperipheral edge portion of the thus folded packaging material or theoverlapped packaging materials is heat-sealed into various heat-sealconfigurations such as side-sealed type, two side-sealed type, threeside-sealed type, four side-sealed type, envelope-sealed type, butt-seamsealed type (pillow-sealed type), pleat-sealed type, flat bottom-sealedtype, square bottom-sealed type and gazette type. The structure of thepackaging bag may vary depending upon contents as well as environmentalconditions and configurations upon use. In addition, the packaging bagmay be in the form of a self-standing bag (standing pouch) or the like.The heat-sealing may be performed by known methods such as bar sealing,rotating roll sealing, belt sealing, impulse sealing, high-frequencysealing and ultrasonic sealing.

The packaging bag is filled with contents through an opening thereof,and then the opening is closed by heat-sealing to produce a packagedproduct using the packaging bag of the present invention.

Examples of the contents to be filled in the packaging bag includeconfectioneries such as rice cookies, bean cakes, nuts, biscuits andcookies, wafers, marshmallows, pies, rare cakes, candies and snacks;staples such as breads, snack noodles, instant noodles, dried noodles,pastas, sterile packaged cooked rice, rice porridges, rice gruel,packaged rice cakes and cereal foods; agricultural processed foodstuffssuch as pickles, boiled beans, fermented soybeans, Miso, frozen beancurd, bean curd, edible fungus (Na-me-ta-ke), Konjak, processed wildplant products, jams, peanut creams, salads, frozen vegetables andprocessed potato products; processed livestock products such as hams,bacons, sausages, processed chicken products and com beefs; processedmarine products such as fish meat hams and sausages, fish-pasteproducts, boiled fish pastes, toasted laver, soy-boiled foods, driedbonitos, salted fish guts, smoked salmons and mustard cod roe;sarcocarps such as peach, orange, pineapple, apple, pear and cherry;vegetables such as cone, asparagus, mushroom, onion, carrot, radish andpotato; cooked foodstuffs, for example, frozen and chilled daily dishessuch as typically hamburgers, meat balls, fried sea foods, dumplingstuffed with minced pork, and croquettes; dairy products such as butter,margarine, cheese, cream, instant creamy powder and childcareconditioned powdered milk; and other foodstuffs such as liquidseasonings, retort curry and pet foods. In addition, the packaging bagcan also be used as a packaging material for tobaccos, disposablethermal body pads, medicines, cosmetics, etc.

The present invention will be described in more detail by reference tothe following examples. However, it should be noted that the followingexamples are only illustrative and not intended to limit the inventionthereto.

(Evaluation Methods)

Oxygen Permeability (cc/m²·day·atm)

The oxygen permeability of the laminated film was measured at 23° C. anda relative humidity of 60% using an oxygen permeability measuring device“OX-TRAN 10/50A” produced by Modern Control Inc. Regarding the oxygenpermeability under high-humidity conditions, it was measured at 23° C.and a relative humidity of each of 80% and 90%.

Oxygen Permeability after Gelbor Treatment (cc/m²·day·atm)

The impact resistance of the laminated film was evaluated after imposinga 360° twist by Gelbor Flex Tester (produced by Rigaku Kogyo Sha Co.,Ltd.) for 500 times, to the laminated film, followed by measuring theoxygen permeability thereof under the condition of the temperature at23° C. and a relative humidity of 60%.

Oxygen Permeability After Retort Treatment (cc/m²·day·atm)

The laminated film was retort-treated at 121° C. for 30 minutes usingRetort Food Autoclave produced by Tomy Co., Ltd., and the oxygenpermeability thereof was measured at 23° C. and a relative humidity of60%.

Water Vapor Permeability (g/m²·day))

The water vapor permeability of the laminated film was measured at 40°C. and a relative humidity of 90% in accordance with a method prescribedin JIS Z-0208.

Appearance

The appearance of the laminated film was visually observed andevaluated.

Initial Tacking Force (g/15 mm)

The laminated film was subjected to T-peel test immediately after thelamination to measure the tacking force thereof at a peel velocity of300 mm/min.

Lamination Strength (g/15 mm)

In accordance with a method prescribed in JIS K-6854, the laminated filmwas subjected to T-peel test to measure the lamination strength thereofat a peel velocity of 100 mm/min.

Heat-Seal Strength (kg/15 mm)

The laminated film was heat-sealed at 160° C. under a load of 2 kg/cm²for one second using a heat-seal treatment apparatus (heat gradienttester) produced by Toyo Seiki Seisakusho Co., Ltd., and a test piece ofthe laminated film was subjected to tensile test at a pulling velocityof 300 mm/min.

(Preparation of Epoxy Resin-Curing Agent)

Epoxy Resin-Curing Agent A

One mole of m-xylylenediamine was charged into a reactor and heated to60° C. under a nitrogen flow, and then 0.80 mol of methyl acrylate wasdropped into the reactor spending one hour. After completion of thedropping, the reaction mixture was stirred at 120° C. for one hour, andfurther heated to 160° C. for 3 hours while distilling off methanol asproduced. Then, the resultant reaction solution was cooled to 100° C.,and a suitable amount of methanol was added to the solution so as toadjust the solid content thereof to 70% by weight, thereby obtaining anepoxy resin-curing agent A.

Epoxy Resin-Curing Agent B

One mole of m-xylylenediamine was charged into a reactor and heated to60° C. under a nitrogen flow, and then 0.90 mol of methyl acrylate wasdropped into the reactor spending one hour. After completion of thedropping, the reaction mixture was stirred at 120° C. for one hour, andfurther heated to 160° C. for 3 hours while distilling off methanol asproduced. Then, the resultant reaction solution was cooled to 100° C.,and a suitable amount of methanol was added to the solution so as toadjust the solid content thereof to 70% by weight, thereby obtaining anepoxy resin-curing agent B.

Epoxy Resin-Curing Agent C

One mole of m-xylylenediamine was charged into a reactor and heated to60° C. under a nitrogen flow, and then 0.95 mol of methyl acrylate wasdropped into the reactor spending one hour. After completion of thedropping, the reaction mixture was stirred at 120° C. for one hour, andfurther heated to 160° C. for 3 hours while distilling off methanol asproduced. Then, the resultant reaction solution was cooled to 100° C.,and a suitable amount of methanol was added to the solution so as toadjust the solid content thereof to 70% by weight, thereby obtaining anepoxy resin-curing agent C.

Epoxy Resin-Curing Agent D

One mole of m-xylylenediamine was charged into a reactor and heated to120° C. under a nitrogen flow, and then 0.33 mol of methyl acrylate wasdropped into the reactor spending one hour. The obtained reactionmixture was stirred at 120° C. for 0.5 hour. Further, after 0.33 mol ofmalic acid was slowly added to the reactor, the obtained reactionmixture was stirred for 0.5 hour and then heated to 180° C. for 3 hourswhile distilling off methanol as produced. Then, the resultant reactionsolution was cooled to 100° C., and a suitable amount of methanol wasadded to the solution so as to adjust the solid content thereof to 70%by weight, thereby obtaining an epoxy resin-curing agent D.

Epoxy Resin-Curing Agent E

One mole of m-xylylenediamine was charged into a reactor and heated to120° C. under a nitrogen flow, and then 0.67 mol of methyl acrylate wasdropped into the reactor spending one hour. The obtained reactionmixture was stirred at 120° C. for 0.5 hour. Further, after 0.33 mol ofacetic acid was dropped into the reactor for 0.5 hour, the obtainedreaction mixture was stirred for one hour and then heated to 180° C. for3 hours while distilling off methanol as produced. Then, the resultantreaction solution was cooled to 100° C., and a suitable amount ofmethanol was added to the solution so as to adjust the solid contentthereof to 70% by weight, thereby obtaining an epoxy resin-curing agentE.

Epoxy Resin-Curing Agent F

One mole of m-xylylenediamine was charged into a reactor and heated to60° C. under a nitrogen flow, and then 0.93 mol of methyl acrylate wasdropped into the reactor spending one hour. After completion of thedropping, the reaction mixture was stirred at 120° C. for one hour, andfurther heated to 160° C. for 3 hours while distilling off methanol asproduced. Then, the resultant reaction solution was cooled to 100° C.,and a suitable amount of methanol was added to the solution so as toadjust the solid content thereof to 70% by weight, thereby obtaining anepoxy resin-curing agent F.

EXAMPLE 1

A 1:1 methanol/ethyl acetate solution (solid content: 30% by weight)containing 50 parts by weight of an epoxy resin having glycidylaminemoieties derived from m-xylylenediamine (“TETRAD-X” available fromMitsubishi Gas Chemical Co., Ltd.) and 115 parts by weight of the epoxyresin-curing agent A was mixed with 0.02 part by weight of an acrylicwetting agent “BYK381” available from BYK Chemie GmbH, and intimatelystirred together to prepare a coating solution.

The thus obtained coating solution was applied over the surface of a 20μm-thick stretched polypropylene film with the use of a bar coater No. 3in a coating amount of 3 g/m² (solid content), dried at 85° C. for 10seconds, laminated with a 30 μm-thick polypropylene film using niprolls, and then aged at 35° C. for one day to obtain a laminated film.It was confirmed that the content of the skeleton structure representedby the formula (1) in the resultant adhesive layer (epoxy resin curedproduct) was 59.5% by weight. The thus obtained laminated film wastested to evaluate a gas barrier property (oxygen permeability and watervapor permeability at a relative humidity of 60%) as well as an initialtacking force and a lamination strength immediately after lamination.The results are shown in Table 1.

EXAMPLE 2

The same procedure as in EXAMPLE 1 was carried out except for using 142parts by weight of the epoxy resin-curing agent B instead of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 59.8% byweight. The thus obtained laminated film was tested to evaluate agas-barrier property, etc. thereof. The results are shown in Table 1.

EXAMPLE 3

The same procedure as in EXAMPLE 1 was carried out except for using 163parts by weight of the epoxy resin-curing agent C instead of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 60.2% byweight. The thus obtained laminated film was tested to evaluate agas-barrier property, etc. thereof. The results are shown in Table 1.

EXAMPLE 4

The same procedure as in EXAMPLE 1 was carried out except for using 110parts by weight of the epoxy resin-curing agent D instead of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 57.4% byweight. The thus obtained laminated film was tested to evaluate agas-barrier property, etc. thereof. The results are shown in Table 1.

EXAMPLE 5

The same procedure as in EXAMPLE 1 was carried out except for using 140parts by weight of the epoxy resin-curing agent E instead of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 59.4% byweight. The thus obtained laminated film was tested to evaluate agas-barrier property, etc. thereof. The results are shown in Table 1.

EXAMPLE 6

The same procedure as in EXAMPLE 1 was carried out except for using 132parts by weight of the epoxy resin-curing agent F instead of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 56.1% byweight.

The thus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. there of. The results are shown in Table 1. In addition,the laminated film was tested for evaluating an oxygen permeabilityunder high-humidity conditions, an oxygen permeability after Gelbortreatment, an oxygen permeability and appearance after retort treatment,and a heat-seal strength thereof The results are shown in Table 2.

EXAMPLE 7

The same procedure as in EXAMPLE 1 was carried out except for using 50parts by weight of an epoxy resin having glycidyl ether moieties derivedfrom bisphenol F (“EPICOAT 807” available from Japan Epoxy Resin Co.,Ltd.) instead of TETRAD-X, and using 141 parts by weight of the epoxyresin-curing agent A, to prepare a laminated film. As a result, it wasconfirmed that the content of the skeleton structure represented by theformula (1) in the adhesive layer of the laminated film was 54.4% byweight. The thus obtained laminated film was tested to evaluate agas-barrier property, etc. thereof. The results are shown in Table 1.

EXAMPLE 8

The same procedure as in EXAMPLE 6 was carried out except for using a 40μm-thick linear low-density polyethylene film instead of the 30 μm-thickpolypropylene film, to prepare a laminated film. The thus obtainedlaminated film was tested to evaluate a gas-barrier property, etc.thereof. The results are shown in Table 1.

EXAMPLE 9

The same procedure as in EXAMPLE 6 was carried out except for using a 15μm-thick stretched nylon film instead of the 20 μm-thick stretchedpolypropylene film, to prepare a laminated film.

The thus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. there of The results are shown in Table 1. In addition,the laminated film was tested for evaluating an oxygen permeabilityunder high-humidity conditions, an oxygen permeability after Gelbortreatment, an oxygen permeability and appearance after retort treatment,and a heat-seal strength thereof. The results are shown in Table 2.

EXAMPLE 10

The same procedure as in EXAMPLE 6 was carried out except for using a 12μm-thick polyethylene terephthalate film instead of the 20 μm-thickstretched polypropylene film, to prepare a laminated film.

The thus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. thereof. The results are shown in Table 1. In addition,the laminated film was tested for evaluating an oxygen permeabilityunder high-humidity conditions, an oxygen permeability after Gelbortreatment, an oxygen permeability and appearance after retort treatment,and a heat-seal strength thereof. The results are shown in Table 2.

EXAMPLE 11

The same procedure as in EXAMPLE 6 was carried out except for using a 50gm-thick paper instead of the 20 μm-thick stretched polypropylene filmand using a 40 μm-thick low-density polyethylene film instead of the 30μm-thick polypropylene film, to prepare a laminated film. The thusobtained laminated film was tested to evaluate a gas-barrier property,etc. thereof. The results are shown in Table 1.

EXAMPLE 12

The same procedure as in EXAMPLE 6 was carried out except for using a 30μm-thick aluminum foil instead of the 20 μm-thick stretchedpolypropylene film, to prepare a laminated film. The thus obtainedlaminated film was tested to evaluate a gas-barrier property, etc.thereof. The results are shown in Table 1.

EXAMPLE 13

The same procedure as in EXAMPLE 10 was carried out except for using a15 gm-thick stretched nylon film instead of the 30 μm-thickpolypropylene film, to prepare a laminated film. Further, the adhesivecoating solution prepared in EXAMPLE 6 was applied over a surface of thenylon film layer of the thus obtained laminated film in a coating amountof 3 g/cm² in terms of its solid content, and dried at 85° C. forseconds. Then, a 40 μm-thick linear low-density polyethylene film waslaminated on the obtained adhesive layer using nip rolls, and theresultant laminated film was aged at 35° C. for one day to prepare alaminated film having a layer structure of polyethylene terephthalatefilm/stretched nylon film/linear low-density polyethylene film.

The thus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. thereof. The results are shown in Table 1. In addition,the laminated film was tested for evaluating an oxygen permeabilityunder high-humidity conditions, an oxygen permeability after Gelbortreatment, an oxygen permeability and appearance after retort treatment,and a heat-seal strength thereof. The results are shown in Table 2.

Comparative Example 1

The same procedure as in EXAMPLE 1 was carried out except for using apolyurethane-based adhesive coating solution composed of an ethylacetate solution (solid content: 30% by weight) containing 50 parts byweight of a polyether component (“TM-329” available from Toyo MortonCo., Ltd.) and 50 parts by weight of a polyisocyanate component(“CAT-8B” available from Toyo Morton Co., Ltd.) instead of the adhesivecoating solution used in EXAMPLE 1, to prepare a laminated film. Thethus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. thereof. The results are shown in Table 1.

Comparative Example 2

The same procedure as in EXAMPLE 1 was carried out except for using 50parts by weight of “EPICOAT 807” instead of TETRAD-X, and using 47 partsby weight of the epoxy resin-curing agent A, to prepare a laminatedfilm. As a result, it was confirmed that the content of the skeletonstructure represented by the formula (1) in the adhesive layer of thelaminated film was 35.7% by weight. The thus obtained laminated film wastested to evaluate a gas-barrier property, etc. thereof. The results areshown in Table 1.

Comparative Example 3

The same procedure as in EXAMPLE 1 was carried out except for using 65parts by weight of an amine-based curing agent as an addition product ofm-xylylenediamine with epichlorohydrin at a molar ratio of about2:1(“GASKAMINE 328” available from Mitsubishi Gas Chemical Co., Ltd.)instead of the epoxy resin-curing agent A, to prepare a laminated film.As a result, it was confirmed that the content of the skeleton structurerepresented by the formula (1) in the adhesive layer of the laminatedfilm was 61.4% by weight.

The thus obtained laminated film was tested to evaluate a gas-barrierproperty, etc. there of. The results are shown in Table 1. In addition,the laminated film was tested for evaluating an oxygen permeabilityunder high-humidity conditions, an oxygen permeability after Gelbortreatment, an oxygen permeability and appearance after retort treatment,and a heat-seal strength thereof. The results are shown in Table 2.

TABLE 1-1 Water vapor Oxygen permeability permeability Appearance (cc/m²· day · atm) (g/m² · day) Example 1 Transparent 8 4 Example 2Transparent 8 4 Example 3 Transparent 10 4 Example 4 Transparent 6 4Example 5 Transparent 8 4 Example 6 Transparent 9 4 Example 7Transparent 14 4 Example 8 Transparent 9 5 Example 9 Transparent 7 12Example 10 Transparent 8 9 Example 11 — 9 10 Example 12 — 0.1 0.1Example 13 Transparent 4 7 Comparative Transparent Less than 1000 4Example 1 Comparative Transparent 68 4 Example 2 Comparative Transparent7 4 Example 3

TABLE 1-2 Lamination strength Initial tacking force (g/15 mm) (g/15 mm)f: PET film broke Example 1 35 30 Example 2 88 30 Example 3 87 32Example 4 40 32 Example 5 32 30 Example 6 100 38 Example 7 45 38 Example8 100 38 Example 9 100 700  Example 10 100  250f Example 11 100 300 Example 12 100 800  Example 13 105 800  Comparative 213 46 Example 1Comparative 40 32 Example 2 Comparative 7 30 Example 3

TABLE 2 Com. Ex. 6 Ex. 9 Ex. 10 Ex. 13 Ex. 6 Oxygen permeability 9 7 8 47 at 60% RH (cc/m² · day · atm) Oxygen permeability 14 12 13 7 14 at 80%RH (cc/m² · day · atm) Oxygen permeability 18 17 17 11 28 at 90% RH(cc/m² · day · atm) Oxygen permeability 11 9 10 4 10 after Gelbortreatment (cc/m² · day · atm) Oxygen permeability 14 10 12 7 18 afterretort treatment (cc/m² · day · atm) Appearance after Trans- Trans-Trans- Trans- Trans- retort treatment parent parent parent parent parentHeat-seal strength 2.6 3.3 3.1 2.6 2.6 (kg/15 mm)

EXAMPLE 14

The same procedure as in EXAMPLE 6 was carried out except for using a 15μm-thick multi-layer stretched nylon film (“SUPERNIEL” available fromMitsubishi Chemicals Corp.; layer structure: nylon-6 (5 μm)/N-MXD6 (5μm)/nylon-6 (5 μm)) instead of the 20 μm-thick stretched polypropylenefilm, and changing the amount of the coating solution applied to 4 g/m²(in terms of solid content), to prepare a laminated film. The thusobtained laminated film was tested to evaluate an oxygen permeabilitythereof. The results are shown in Table 3.

Comparative Example 4

The same procedure as in EXAMPLE 14 was carried out except for using thepolyurethane-based adhesive coating solution used in COMPARATIVE EXAMPLE1 instead of the adhesive coating solution used in EXAMPLE 14, andchanging the amount of the coating solution applied to 2 g/m² (in termsof solid content), to prepare a laminated film. The thus obtainedlaminated film was tested to evaluate an oxygen permeability there of.The results are shown in Table 3.

EXAMPLE 15

The same procedure as in EXAMPLE 6 was carried out except for using a 15μm-thick unstretched EVOH film (ethylene content: 32 mol %) instead ofthe 20 μm-thick stretched polypropylene film, and changing the amount ofthe coating solution applied to 4 g/m² (in terms of solid content), toprepare a laminated film. The thus obtained laminated film was tested toevaluate an oxygen permeability thereof. The results are shown in Table3.

Comparative Example 5

The same procedure as in EXAMPLE 15 was carried out except for using thepolyurethane-based adhesive coating solution used in COMPARATIVE EXAMPLE1 instead of the adhesive coating solution used in EXAMPLE 15, andchanging the amount of the coating solution applied to 2 g/m² (in termsof solid content), to prepare a laminated film. The thus obtainedlaminated film was tested to evaluate an oxygen permeability thereof.The results are shown in Table 3.

TABLE 3 Com. Com. Ex. 14 Ex. 15 Ex. 4 Ex. 5 Oxygen permeability at 60%RH 3 0.6 6 0.6 (cc/m² · day · atm) Oxygen permeability at 80% RH 5 4 8 6(cc/m² · day · atm) Oxygen permeability at 90% RH 8 14 15 60 (cc/m² ·day · atm)

EXAMPLE 16

Two laminated films prepared in EXAMPLE 6 were overlapped so as to facetheir polypropylene film layers to each other, and the outer peripheraledge portions of the overlapped films were heat-sealed at three sidesthereof to produce a three side-sealed type packaging bag having anopening on its upper side.

The thus produced packaging bag was filled with a nitrogen gas, and thenclosed by heat-sealing the opening side thereof. The closed packagingbag was preserved at 23° C. for one week in air under such anenvironmental condition that both inside and outside of the bag wereexposed to 60% RH. Thereafter, the packaging bag was subjected to gaschromatography to measure an oxygen concentration inside of the bag,thereby determining an oxygen permeability of the laminated film. Theresults are shown in Table 4.

EXAMPLE 17

Two laminated films prepared in EXAMPLE 9 were overlapped so as to facetheir polypropylene film layers to each other, and the outer peripheraledge portions of the overlapped films were heat-sealed at three sidesthereof to produce a three side-sealed type packaging bag having anopening on its upper side.

The thus produced packaging bag was subjected to the same procedure asin EXAMPLE 16 to measure an oxygen concentration inside of the bag andan oxygen permeability of the laminated film. The results are shown inTable 4.

EXAMPLE 18

Two laminated films prepared in EXAMPLE 10 were overlapped so as to facetheir polypropylene film layers to each other, and the outer peripheraledge portions of the overlapped films were heat-sealed at three sidesthereof to produce a three side-sealed type packaging bag having anopening on its upper side.

The thus produced packaging bag was subjected to the same procedure asin EXAMPLE 16 to measure an oxygen concentration inside of the bag andan oxygen permeability of the laminated film. The results are shown inTable 4.

TABLE 4 Oxygen concentration inside of bag Oxygen permeability (cc/bag ·one week) (cc/m² · day · atm) Example 16 0.48 16 Example 17 0.27 9Example 18 0.40 13

As is apparent from the measurement results shown in Table 4, thepackaging bag of the present invention reveals a substantially excellentoxygen-barrier property. In addition, as is apparent from the results ofevaluation of properties, the packaging bag of the present invention hasexcellent heat-seal strength and lamination strength. Therefore, thepackaging bag of the present invention can be suitably used as a bag forpackaging contents for which a high oxygen-barrier property is required,such as foods and medicines.

INDUSTRIAL APPLICABILITY

The adhesive for laminates according to the present invention can revealnot only a suitable adhesion property to various film materials but alsoa high gas-barrier property, so that it is possible to achieve acombined function as gas-barrier layer and adhesive layer by only onelayer produced therefrom.

As a result, although the conventional packaging laminated film isrequired to separately provide a gas-barrier layer and an adhesive layerformed between the gas barrier layer and a sealant layer, the use of theadhesive for laminates according to the present invention makes itpossible to obtain a laminated film for packaging material having a highgas-barrier property without separately forming a gas-barrier layer.Further, the adhesive for laminates according to the present inventionmay also be used as an adhesive layer for bonding the conventionalgas-barrier film made of PVDC coating layer, polyvinyl alcohol (PVA)coating layer, ethylene-vinyl alcohol copolymer (EVOH) film layer,m-xylyleneadipamide film layer and inorganic deposited film depositedwith alumina (Al₂O₃) or silica (Si) to a sealant layer, thereby enablingproduction of a laminated film revealing a more remarkably improvedgas-barrier property. In addition, when the conventional gas-barrierfilms having such a problem that the gas-barrier property thereof isgenerally deteriorated under high-humidity conditions, are used incombination with the adhesive for laminates according to the presentinvention, it becomes possible to overcome the problem.

Also, the laminated film prepared using the adhesive for laminatesaccording to the present invention as well as the packaging bag producedby forming the laminated film into a bag shape, are excellent in notonly gas-barrier property such oxygen- barrier property or watervapor-barrier property but also lamination strength and heat-sealstrength, and reveal suitable mechanical, chemical or physical strength,for example, excellent fastness properties such as heat resistance,.water resistance, aroma retention property, light resistance, chemicalresistance, piercing resistance and various other properties. As aresult, according to the present invention, there can be provided apackaging material capable of sufficiently protecting contents to befilled or packaged therein, for example, foods such as confectioneries,staples, processed agricultural products, processed livestock products,processed marine products, sarcocarps, vegetables, cooked foodstuffssuch as frozen and chilled daily dishes and liquid seasonings;cosmetics; drugs; or the like, and exhibiting excellent storage andkeeping stability, filling and packaging capabilities, etc.

1. An adhesive for laminates containing an epoxy resin compositioncomprising an epoxy resin containing glycidylamine moieties derived fromm-xylylenediamine and an epoxy resin-curing agent, the epoxy resincomposition being formed into an epoxy resin-cured product containing askeleton structure represented by the formula (1):

in an amount of at least 40% by weight, wherein the epoxy resin-curingagent is a reaction product of m-xylylenediamine with at least oneselected from the group consisting of acrylic acid, methacrylic acid anda derivative thereof, wherein a blending ratio between the epoxy resinand the epoxy resin-curing agent in the epoxy resin composition is suchthat an equivalent ratio of active hydrogen contained in the epoxyresin-curing agent to epoxy groups contained in the epoxy resin fallswithin the range of 0.8:1 to 1.4:1, and wherein a molar ratio of the atleast one selected from the group consisting of acrylic acid,methacrylic acid and a derivative thereof to the m-xylylenediamine fallswithin a range of 0.8:1 to 0.97:1.
 2. The adhesive according to claim 1,wherein the epoxy resin-curing agent contains amido groups in an amountof at least 6% by weight based on a total amount of the curing agent. 3.The adhesive according to claim 1, wherein a laminated film preparedusing the adhesive has an initial tacking force of 30 g/15 mm or higheras measured between film materials thereof by subjecting the laminatedfilm to T-peel test at a peel velocity of 300 mm/mm immediately afterthe lamination.
 4. An adhesive assistant comprising the adhesive asdefined in claim 1.